Corydalis sunhangii (Papaveraceae): A new species from Xizang, China, based on plastome and morphological data

Abstract A new species of Papaveraceae, Corydalis sunhangii, in the section Trachycarpae, is described and illustrated from Nyingchi City, Xizang, China. The new species has some resemblance to Corydalis kingdonis, but differs by radical leaves prominent, usually several, blade tripinnate (vs. insignificant, few, blade bi‐ to triternate); cauline leaf usually one, much smaller than radical leaves, usually situated in lower half of stem (vs. usually two, larger than radical leaves, concentrated in upper third of stem); racemes densely 13–35‐flowered (vs. rather lax, 4–11‐flowered); claw of lower petal shallowly saccate (vs. very prominently and deeply saccate); capsule oblong, with raised lines of dense papillae (vs. broadly obovoid, smooth). Phylogenetic analysis, based on 68 protein‐coding plastid genes of 49 samples, shows that C. sunhangii is not closely related to any hitherto described species, which is consistent with our morphological analysis.


| INTRODUC TI ON
The genus Corydalis DC. in Lamarck & De Candolle (1805: 637), the largest genus of Papaveraceae, contains ca.530 species (Chen et al., 2023) mainly distributed in the North Temperate zone with the highest diversity in China (Wu et al., 1999;Zhang et al., 2008).The name Corydalis has a very checkered history.Linnaeus (1737Linnaeus ( , 1753) ) treated all species of the subfamily Fumarioideae in a single genus Fumaria.His original 11 species are now distributed among nine different genera.The first modern user of the generic name Corydalis was Medikus (1789), picking up an old name from Dillenius (1719), for a South African genus.However, this genus had already been named Cysticapnos by Miller (1754).Then Ventenat (1803) used Corydalis to refer to the species now called Capnoides sempervirens (L.) Borkh.and Adlumia fungosa (Aiton) Britton.During the 19th century, Corydalis came to refer to any Fumarioideae with zygomorphic flowers and many-seeded capsules.However, according to the principle of priority, Corydalis would be a synonym of Cysticapnos, and Corydalis in the modern sense should be called Pistolochia (Bernhardi, 1800).If the genus name Pistolochia was used, it will inevitably cause many name changes.To stabilize the situation, Corydalis was therefore proposed for conservation by Mansfeld (1953).He, however, unfortunately chose the sole species of Capnoides Mill.(C.sempervirens) as type for the conserved name, thereby making things even worse.This was eventually rectified (Lidén, 1981) to allow for continuation of the established use of Corydalis, with the conserved type C. solida (L.) DC.
And Lidén (1981)  Previous molecular analyses, based on few molecular markers and incomplete taxonomic sampling, were clearly inadequate to delimit sections and subgenera (Lidén et al., 1995(Lidén et al., , 1997;;Wang, 2006;Xu et al., 2022).Recently, Chen et al. (2023) proposed a new classification of Corydalis with four subgenera and 39 sections, based on 65 protein-coding plastid genes and 152 universal low-copy nuclear genes, using samples covering all previously recognized sections and independent "series." China has a vast territory with a wide range of complex and diverse topographies and soils and covering several climate types (Chen et al., 2020), which contribute to the high species diversity of Corydalis.The Himalaya-Hengduan Mountains region is the diversity center of Corydalis (Wang, 2006).Recently, we discovered a species of Corydalis, collected from Sejila Mountain in Nyingchi City, which did not agree with any previously known species.
Located in southeast Xizang, west of Nanga Bawa Peak, Sejila Mountain is a watershed between the Niyang River and the Palong Zangbo River, and the highest elevation of Sejila Mountain is about 5300 m (Luo et al., 2021).
Our new species belongs to Corydalis sect.Trachycarpae (Fedde) Fedde, characterized by fasciculate fleshy storage roots, reflexed fruiting pedicels, and corolla often with distinct dark veins.The section name Trachycarpae also has a checkered history.This name as no formal rank stated "Gruppe" was first proposed by Fedde (1924).Subsequently, sect.Trachycarpae was officially established by Fedde (1936), who selected C. trachycarpa Maxim.as type for this section.However, this section name was often used as synonym of sect.Fasciculatae (Lidén, 1986;Wu et al., 1999).In 1889, Maximowicz established sect.Fasciculatae Maxim.and in sect.Fasciculatae, C. curviflora Maxim.as well as from the remotely related sect.Trachycarpae (e.g. C. trachycarpa) were included (Maximowicz, 1889).However, he did not designate a type.The first publication in which a type is designated for sect.Fasciculatae is Lidén (1986), who selected C. cashmeriana Royle (an earlier described species, which is referred to by Maximowicz as closely related to C. curviflora) as "type," which amounts to an "inadvertent lectotypification" according to §7.11 of the Code (Turland et al., 2018).However, Wu et al. (1999), instead designated C. trachycarpa as "type" for sect.Fasciculatae, presumably unaware of the earlier action by Lidén. And Wu et al. (1999) used sect.Fasciculatae as official name for this section and sect.
Trachycarpae as a synonym for this section, and recorded 17 species and five varieties, which belong to two different sections according to Chen et al. (2023).However, Zhang et al. (2008) adopted sect.
Trachycarpae as the official name for this section group and recorded 52 species.From then on, sect.Trachycarpae as official name was stable and widely accepted.Afterward, there were three new species published in this section (Lidén et al., 2013;Pathak et al., 2013).

Corydalis dorjii D.G.Long and C. lupinoides C.Marquand & Airy Shaw
previously included within sect.Trachycarpae in Zhang et al. (2008) were removed from this section and belong to sect.Lupinoides J.T. Chen, T. Deng, Lidén & H. Sun in Chen et al. (2023).Corydalis milarepa was wrongly placed in sect.Chrysocapnos Wendelbo in Zhang et al. (2008) for the type specimen had no roots, and these species were moved into this section in Chen et al. (2023).According to Chen et al. (2023), there are 55 species in this section, of which 52 species occur in China, including 47 endemics.It is one of three sections in Corydalis that have over 50 species (Chen et al., 2023).Our new species is not closely similar to any other known species, and it is described below as Corydalis sunhangii J.T. Chen, T. Deng & M. Lidén.

| Morphological comparison
Specimens of Corydalis sunhangii were collected from Nyingchi City in Xizang and studied at the herbarium of KUN, UPS, and HNWP.Morphological characters, recorded for the new species, were based on dried specimens and photographs.

| Phylogenetic reconstruction
Our molecular analysis was performed based on 49 samples (includ-  Vouchers are deposited in the herbaria KUN and PE.Vouchers information for new sequences are presented in Table 1. Based on Chen et al. (2023), we chose 68 shared proteincoding plastid genes to perform the phylogenetic analysis.All sequences were obtained from the genome skimming data.DNA extraction, library preparation, and sequencing were conducted at Novogene (Beijing, China).The sequencing reads were assembled using GetOrganelle v1.7.4.1 (Jin et al., 2020).All linear chloroplast genomes were annotated using PGA (Qu et al., 2019).The plastid genes were aligned using MAFFT version 7.475 (Katoh & Standley, 2013), followed by minor manual corrections.Gaps were treated as missing data.
Substitution model options were set to auto, followed by 1000 bootstrap replicates.The best-fit model TVM + I + G estimated in jMod-elTest (Posada, 2008) using Bayesian information criterion (BIC) for Bayesian inference (BI) analysis.BI tree was conducted by MrBayes version 3.2.7 (Ronquist & Huelsenbeck, 2003) using the settings: Bayesian trees were started from random trees; four Markov Chain Monte Carlo (MCMC) simulations were run simultaneously and sampled every 1000 generations for a total 2 million.Runs were considered to have converged to stationarity when their average standard deviation of split frequencies was less than 0.01 and the first 25% trees were discarded as burn-in.

| Morphology
In sect.Trachycarpae, there are some species with rather smaller yellow flowers with inner petals with sharply contrasting black-purple  2 (Figure 1).

| Molecular phylogenetic analysis
The length of the concatenated 68 plastome CDS from 49 samples was 56,935 bp, of which 37,816 sites were constant (66.4%).Of

| DISCUSS ION
The monophyly of sect.Trachycarpae based on 68 plastome CDS from 45 plastomes is congruent with previous study (Chen et al., 2023) based on the combined 65 plastome CDS and 39 plastomes of sect.
Trachycarpae.Here, the most comprehensive and robust phylogeny of sect.
proposed Corydalis DC. in Lamarck & De Candolle (De Candolle, 1805) as the initial document of Corydalis.
ing 5 newly sequenced) from 41 species and represents the most comprehensive phylogeny of sect.Trachycarpae so far.Corydalis inopinata Prain ex Fedde, C. pseudodrakeana Lidén, and C. lupinoides were chosen as outgroups, based on results of Chen et al. (2023).
apex that are similar to C. sunhangii.We have selected C. kingdonis Airy Shaw for the morphological comparison, as it shares some general attributes with C. sunhangii, and has an adjacent distribution.It is fairly frequent around Duoxiongla on the south side of the Yarlung Zangbo River and at Galongla a bit further East.C. juncea Wallich is distributed in the central and eastern regions of the Himalayas, further away from this new species.Morphological comparisons of C. sunhangii, with the slightly similar taxa C. kingdonis and C. juncea are provided in Table these 68 plastome CDS, 60 CDS covered 49 individuals, five CDS covered 48, and three CDS covered 46.Based on 68 shared protein-coding plastid genes, BI and ML trees were reconstructed and their topologies are similar (Figure 2).The phylogenetic analyses show that all 45 samples of sect.Trachycarpae clustered into one clade with strong support (BIPP = 1, MLBS = 100%).Its sister group is C. sect.Inopinatae represented by C. inopinata Prain ex Fedde.Agreeing with previous analyses (Chen et al., 2023), C. juncea is sister to the rest of the sect.Trachycarpae in both trees.Both trees also show that our two accessions of the new species grouped together (BIPP = 1, MLBS = 100%) and form a sister group to the clade consisting of the remaining 42 samples of the section with high support (BIPP = 1, MLBS = 100%).
, C. homopetala Diels, C. bijiangensis C. Y. Wu et H. Chuang, C. weisiensis H. Chuang, C. lopinensis Franch.)havesome similar morphological features, such as rather smaller yellow flowers with inner petals with sharply contrasting black-purple apex, but the phylogenetic results suggest that these characters are plesiomorphic, that is, which do not indicate that these species sharing them are related.In the phylogeny of sect.Trachycarpae, this new species does not have a truly related sister species and adjacent to the new species are two isolated Phylogeny of Corydalis sect.Trachycarpae based on the combined 68 plastome CDS.Numbers above branches indicate Bayesian posterior probability (BIPP), numbers below branches represent maximum likelihood bootstrap support (MLBS).The new species is shown in bold.CHEN et al.is also similar to C. juncea and C. kingdonis in having small yellow flowers with inner petals with sharply contrasting black-purple apex, but differs in having tripinnate radical leaves, different cauline leaves, densely 13-35-flowered racemes, unique flowers and oblong capsules with raised lines of dense papillae.Considering the morphological data and phylogenetic results, we believe that this evidence satisfies the required diagnostic criteria to identify C. sunhangii as a new species.Corydalis sunhangii resembles C. kingdonis, but differs by its radical leaves prominent, usually several, blade tripinnate (vs.insignificant, few, blade bi-to triternate); cauline leaf usually one, much smaller than radical leaves, usually situated in lower half of stem, ovate, bipinnate, pinnate, or palmatisect (vs.usually two, like radical leaves but larger, in upper third of stem, blade bi-to triternate); racemes 3-7 cm, densely 13-35-flowered (vs.1.5-2.5 cm, rather lax, 4-11-flowered); claw of lower petal shallowly saccate (vs.very prominently and deeply saccate); capsule oblong, with raised lines of dense papillae (vs.broadly obovoid, smooth).